This invention relates to the forming of miniature mold cavities for molding small features integral with a base sheet, and has particular application to the production of touch fasteners and the like.
Touch fastener products have arrays of miniature fastener elements (for instance, hook-shaped or mushroom-shaped elements) extending from a common base. Typically, in order to be capable of engaging a loop fiber or another fastener element, these fastener elements have overhanging "crooks", such as the hook portion of a hook-shaped element or the underside of the head of a mushroom-shaped element. These crooks snag and retain loop fibers, for instance, to form a fastening, but can be challenging to mold in their fully functional form in non-opening mold cavities.
One solution for continuously molding such fastener elements for touch fasteners and other products was disclosed by Fischer in U.S. Pat. No. 4,794,028. In commercial implementations of his solution, a cylindrical, rotating mold roll is composed of a large number (e.g., thousands) of thin, disk-shaped mold plates and spacer plates which are stacked concentrically about a central barrel. Extending inwardly from the periphery of the mold plates are cavities for molding the hook elements. These mold cavities are composed of contoured mold surfaces in the mold plates in combination with flat side surfaces of adjoining spacer plates. To produce mold plates for current production machines, each contoured mold surface is typically formed by electro-discharge machining (EDM) methods.